Local broadcasters control valuable spectrum that could be leased to wireless operators. Why Sinclair and Nexstar could be worth as much as twice their current quotes.

Something quaint is happening in TV land. Amid all the talk about new technologies for delivering video, it's the local broadcasters—the companies that carry local news and sitcom reruns—that are stealing the show.

Shares of Nexstar Broadcasting Group (ticker: NXST), an operator of 72 local TV stations, are up 254% in 2013. The surge bests even the torrid pace of Netflix (NFLX), the leading proxy for TV's hyped future. Sinclair...